Shahram Mori (smori at nmsu.edu) wrote:
: dear immunetters
: I have seen very interesting posts on B7-1 and B7-2 by Lee Wetzler and thierry
: sornasse. However I am still a little confused on a couple of experiments that
: they did to get at B7-2. My first point of confusion is that if B7-2 is the
: major costimulatory protein then what is the function of B7-1 ( since its
: m RNA is not even produced till about 24-48hrs after the first signal is
: received by the T cell in which case would be to differentiate)?
: There could be a couple of possibilities.
: 1) B7-1 is stimulated under different conditions than B7-2 and that's the
: reason for the group seeing low b7-1 under those conditions.
: 2) B7-1 has other purposes activation is not its major role.
: My second point of confusion was that just knowing that B7-1 is not
: produced early enough one can't assume that
: 1) B7-1 is not the major co-stimulatory signal, because different antigens
: might preferentially induce one or the other of B7's.
: 2) Just because B7-2 is produced early that it's the major factor. Because we
: all know that there are translational regulations and post translational
: modifications that might be going on and this might affect the expression
: of B7-2.
: If B7-1 and B7-2 do have the same function then why is it necessary to have
: both?
: Thanks again for everybody that responded to my " new discussion in
: immunology" post.
: Cheers
: ShahramI guess posting is better so everyone who is interested can read it.
: _/\_
: _\ /_
: \_ _/
: ||
Well, these questions are actually the basic questions that now need to be
asked regarding costimulation and the various costimulation counter-
receptors. As pointed, out, the supposed importance of B7-2 is because of the
timing and amount of B7-2 expression. But remember, this is still IN VITRO
data. The in vivo experiments are to be done. The groupd at harvard
(G. Freedman, A. Sharpe) originally made the B7 minus mice, but are working on
B7-2 deficinet mice. That will certainly help to differentiate the
function of each ligand. Most likely both will be proved to be important,
since inhibiting one with specific mAb only decreases T lc costim by 50% or
so.
I do agree though that B7 and B7-2 expression are differentially stimulated,
I have experiments with this exact finding, B7-2 expression increasing without
B7 expression changing, but this shall depend on what stimulus is used.
THis all shows the big black box immunology really is, and we are all
still just scratching the surface, the best way we know how.
Lee
______________________________________ _________________________________
[ Lee Wetzler || ]
[ The Maxwell Finland Laboratory || e-mail lwetzler at acs.bu.edu ]
[ for Infectious Diseases || ]
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